The recent trend of miniaturization and performance-advancement of electronic apparatus demands further increase in the scale of integration and further enhancement of functions of various LSICs represented by ASICs. Such demand requires the development of semiconductor device fabricating techniques capable of forming a processed layer on a wafer in higher planarity meeting quality requirements.
A technique of forming a multilayer structure having a planar surface including a processed layer and an insulating layer on a wafer is disclosed in U.S. Pat. No. 5,597,668. This technique uses a photomask provided with a dummy pattern (also referred to as “additional pattern”) for forming pattern elements that do not participate in forming a circuit (hereinafter referred to as “dummy pattern elements”).
Such a dummy pattern included in a photomask contributes to forming further planar processed layer on a wafer.
A photomask provided with such a dummy pattern (photomask with a dummy pattern) is formed by using pattern data including dummy pattern data. An inspection instrument inspects a photomask for defects by comparing the photomask with pattern data including dummy pattern data and decides that parts represented by data that does not coincide with the pattern data are defective.
When a photomask formed by using pattern data including dummy pattern data is inspected, the sensitivity of defect detection has been raised to cope with the increased density and advanced miniaturization of pattern elements.
The inspection instrument is set for a predetermined defect-detecting sensitivity. Usually, the defect-detecting sensitivity is defined on the basis of the size of detected defects.
A method of inspecting a photomask with a dummy pattern formed on the basis of the pattern data including dummy pattern data inspects also the dummy pattern, whose defects do not cause any problem in the circuit, at an unnecessarily high defect detection level. Therefore, parts that are determined to be defective of the dummy pattern must be examined, which affect adversely to the efficiency of inspection.
Although residual defects are removed by using a laser beam or an ion beam and vacancy defects are mended by focused-ion-beam-assisted CVD or the like, it is difficult to correct those defects completely. Thus, defects are detected sometimes when the corrected photomask is inspected again. The inspection of the photomask is performed again at an unnecessarily high defect detection level.
The conventional photomask inspecting method of inspecting a photomask for defects inspects the dummy pattern, whose defects do not cause any problem in the circuit, at an unnecessarily high defect detection level. Therefore, parts that are determined to be defective of the dummy pattern must be examined, which affect adversely to the efficiency of inspection.